High-frequency signaling system



Aug..'17,192 6. 1,596,101

- W. H. T. HOLDEN ET AL Fild Nov. 17, 1924 F J INVENTORS -'Q rim/W521: ilficluumm Patented Aug.'17, 1926.

UNITED STATES PATENT OFFICE.

WILL! I. T. HOLDEN AND FRED WILLIAM SGHRAMM, bl BROOKLYN, NEW YORK, ABSIGNOBS TO AMERICAN TELEPHONE AND TELEGRAPH OOKPANY, A CORPORA- TION 0] NEW YORK.

HIGH-FREQUENCY SIGNALING. SYSTEM.

Application fled November 17,1924. Serial No. 750,869.

This invention relates to signaling systems, and particularly to means for deriving from analternating current source the necessary unidirectional current for the proper operation of vacuum tubes and also for a microphone or other apparatus.

In the copending application of W. H. T. Holden, Serial No. 749,791, filed November 13, 1924, is disclosed a method and means for utilizing an alternating current source for providing the unidirectional potentialsand currents necessary for the proper operation of vacuum tubes. In the system therein disclosed the space current flowlng from the plates to the filaments of th e power amplifier tubes is utilized for energlzmg the filaments of detector tubes. The space current of the power amplifier tubes 15 derived by rectifying an alternating current. This space current is particularly well suited for heating the filaments of the detectors, because after initial rectification and filtering it has been passed through the windings of the output transformers of the power amphfiers, which by virtue of their high inductance tend to further exclude any alternating components that may be present in the space current.

This invention resides in a method and means whereby the normal current required for a microphone may be derived from the space current of an amplifier, which, space current is provided by the rectification of alternating current; and, whereby abnormal current requirements of the microphone are cared for directly from the rectifier which supplies the unidirectional current to the tubes of the amplifier.

This invention will be clearly understood from the following description when read in connection with the attached drawing showing schematically a form of embodiment of the invention.

In thedrawing the line L represents a source of alternating current as for example, a 110-volt houselighting system. This source is connected with a rectifier by means of the transformers T and T The line L is also connected with a transformer T for the purpose of energizing the filaments of the vacuum tubes of the power amplifier, which operation will later described in detail. The rectifier comprises in part the tubes R and R the filaments of both of which are connected with the secondary winding of transformer T in order to derive the necessary heating current. Transformer T serves to impress upon the rectifier the alternating current that is to be rectified. As will be seen, one of the outer terminals of the secondary winding of T is connected with the anode of rectifier R and the other outer terminal of the secondary winding is connected with the anode of tube R The midpoint of this winding is connected with the output circuit of the rectifier and constitutes the negative side of that circuit. The positive side of the output circuit is connected with the plates of the tubes A to A inclusive. Connected with the output circuit are the low-pass filters F, and F comprising a plurality of series inductances and shunt capacities, which are so proportioned as to sub stantially suppress any alternating current components that may be resent in the output circuit of the recti er. The positive conductor joining filters F, and F is connected by means of conductors 1 and 2 with the midpoint of the primary windin of transformer T the terminals of w ich winding are connected with the plates of the tubes A and A constituting the first stage of'the push-pull amplifier. The circuit just traced provides for the application of the positive potential to the plates of the said tubes. In like manner a positive. direct potential is applied to the plates of tubes A and A over conductors 1 and 3, which is connected with the midpoint of the primary winding of transformer T The tubes last mentioned constitute the second stage of the said push-pull amplifier. The filaments of all of the tubes of this ampli-- fier are rendered active by current derived from the alternating current sourcellz through the transformer T The secondary winding of transformer T is connected with the output circuit L so that the amplified currents will be impressed thereon. A microphone M is connected with the push-pull amplifier by the transformer T which has its primary winding connected with the microphone circuit and its'secondary winding connected with the amplifier. The outer terminals of the primary winding of transformer T, are connected with the buttons of the microphone. The diaphragm is connected by conductors 4 and 5 with the negatlve side of thefilter F The midpoint of the primary winding of T is connected not only with the positive side of the filter F but is also connected by conductor 6 with the midpoint of the secondary winding of transformer T,. This conductor has .in series therein an inductance 7, and has also in parallel therewithi a condenser 8. The func-v tion of the inductance 7 and condenser 8 is to exclude'any alternating current component that may be present in the space current of the amplifier tubes, from getting into the microphone circuit. phragm of the microphone is also connected by conductors 4 and 9 to ground. The necessary negative potential for the grids of the tubes of the amplifier is provided by the batteries B, and B which are grounded at the point 10. It is to be understood, how-' ever, that the necessary'grid biasing potential for the operation of these tubes could be derived in the same manner 1n Wl'llCh 1t is derived in the system shown in the copending application of Holden, referred to hereinbefore.

From the foregoing description of the circuit in which the invention is embodled it will be seen thatwhen an alternating potential is impressed upon the line L the filaments of the rectifying tubes ,R, and R will be energized through the transformer T, and the alternatingcurrent through the transformer T will be rectified so that a d1- rect potential will be impressed across the output circuit of the rectifier. At the same time the filament of the tubes A, to A 1nclusive, of the amplifier, will be energized through the transformer T When the filaments of the amplifier tubes are energized and a positive potential has been applied to the plates of the said tubes from the positive side of the output circuit of the rectifier through the low-pass filter F,, through conductors 1 and 2 to the plates of A, and A and through conductors 1 and 3 to the plates of A and A a space current will flow from the positive side of the rectifier output cir-' cuit over conductors .1, 2 and 3, through the micr.0phone M,,

evacuated space between the plates and the filaments of the tubes, thence over conductors 11 and 12 in parallel to the secondary winding of transformer T to the midpoint thereof, thence over conductors 6 and 13 to the midpoint of the primary winding of transformer T thence through conductors 14 and 15 in parallel to and through the thence over conductors 4 and 5 to the negative side of filters F and F The space currents of the type of tubes normally used in power amplifiers would be The diabe rents of the said tubes sufficient to supply the normal operating current for the microphone M,. In order to provide for a current in excess of that normally required, the output circuit of the rectifier is connected directly with the microphone circuit through the filters F, and F This connection is in parallel with the circuit through which the space current of the ampliftier was suppliedto the microphone circu1 Y It will accordingly be seen that by means of our invention the space current of the amplifier is used to supply the normal operating energy of the microphone. This current is singularly free from any alternating current components not only because it has been passed through the filter F, but also cause of the high inductance of the primary windings of the transformers T, and T, through which it passes to the plates of the ampllfier tubes. .The excess current requirement of the microphone circuit is cared for by the direct connection between the rectifier and the microphone circuit through the filters F, and F Such an arrangement provides not only for the operation of vacuum tubes but also a microphone from an alter nating current source.

ile this invention has been disclosed schematically in a certain form, it is to be understood that it is capable of embodiment in other and different forms without departing from the spirit and scope of the appended claims.

at is claimed is In an amplifying system, the combinarality of tubes of a source of alternating current, a rectifier connected with the said source, a microphone, means for energizing the filaments of the amplifier tubes with alternating current, means for applying a rectified voltage to the plates of the amplifier tubes, and means for utilizing the space curto energize the microphone.

2. In an amplifying system, the combination with a push-pull amplifier having a plurality of tubes of a source of alternating current, a rectifier connected with the said source, a microphone, means for energizing the filaments of the amplifier tubes with alternating current, means for a plying a rectified voltage to the plates of the amplifier tubes, means for of the said tubes and a secondary phone consisting tween the rectifier and the said microphone. 3. In an amplifying system, the combination with a vacuum tube amplifier of a microphone connected therewith, a source of means to energize the filaments of the vaccro'pho'ne compr' a connection between uum trained the amplifier by alternating the said filter and t e said microphone. current, means to impress the rectified volt- Intestimony whereof we have signed our 1 age upon the late of the said tube, means names to this specification this 14th day of l for utilizing t e space current of the tubes November, 1924.

to energize the microphone, and a secondary WILLIAM H. T. HOLDEN. source of energizing current for the said m1- FRED WILLIAM SGHRAMM. 

